242 THE UNIVERSITY SCIENCE BULLETIN. 
C. Check. 
a. Boil some of the surveyed culture to kill organisms. 
1. Place carmine over this in stender and repeat the series under 
Bb. 
Culture 17129 was made by grinding water-soaked leaves of 
dead Typha. These grindings had reached a state of balance 
before using in this experiment. It had been used to rear 
Corixids and so was known to contain the essential elements 
of the boatman food supply. A survey of the culture is given 
elsewhere, but it is well to recall that it consisted of ground- 
up bits of Typha tissue, a few Englenids, some Tetraspora, | 
some algal filaments, live and dead rotifers, about equally 
divided, some nematode worms, and here and there various 
protozoans. 
Some carmine was then sprinkled over a layer of this ma- 
terial in a stender and allowed to stand for 24 hours to note the 
effect of the carmine upon the animal organisms. The animals 
were alive and the nematodes and rotifers and some of the pro- 
tozoa contained carmine, not in considerable quantities, how- 
ever. One dead Oligocheta was quite strongly stained. 
Adult Corixids of the species Palmacorixa buenoi, after 12 
hours in clear water, were placed on this carmine forage, and 
began feeding at once. By the end of ten minutes the anterior 
end of the stomach of one af them was carmine red. Besides 
carmine grains, there were present some rotifer skins, one with 
red in it, open jaws of rotifers, and some green Englenids. 
Other specimens show the presence of considerable carmine 
mixed with plant matter some alge filaments, and here and 
there a nematode. In all, the digestive tracts were filled with 
red matter, a little of which could be traced directly to the 
animals consumed. The colored drawing of a nematode shows 
one source of the carmine. 
To determine whether Corixids were after live animals or — 
would eat dead ones, too, some of the Typha was cooked. An 
examination showed dead rotifers and worms, etc. Added car-— 
mine to this, with the idea that the animals being dead could © 
not ingest it. Corixids began foraging at once. An examina- 4 
tion of their stomachs showed that they were taking up plant — 
matter and carmine grains, also some of the dead rotifers, etc. 
After a few hours the dead animals had taken up the stain and 
in this way would account for some of the red in the Corixids, 
